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Wieters is coming off a 4.3 WAR season in 2011 with a jump in power and relatively low BABIP. 2012 could be his breakout year. Its likely Wieters' hitting ceiling is a bit lower than originally expected, but hes had 2.5 years of MLB time and is still an impact player.
If Bal had transitioned Wieters to DH in his rookie season and gotten his 2011 hitting line last year (Cs develop later than 1B/DH), they would have been rewarded with a mediocre 1-1.5 Win DH.
I don't think Wieters is an example of why you should move tweener Cs off to 1B/DH early in their careers. Hes the exact opposite. Thanks to sticking at C hes turned into an impact player. If he were a DH-only, its likely that he'd have very little value right now.